Dimensional stabilizing process

Abstract

A method of dimensionally stabilizing a transparent, shrinkable thermoplastic layer, such as polyethylene terephthalate, in a draw-formed laminate with plasticized polyvinyl butyral which comprises heat setting the thermoplastic layer.

We claim: 
     
       1. A method of dimensionally stabilizing a transparent, shrinkable thermoplastic layer in a draw-formed laminate, said thermoplastic layer carrying one or more performance layers or coatings and being bonded in the laminate with layers of plasticized polyvinyl butyral, said process comprising heat setting the thermoplastic layer by heating the laminate while holding the laminate against the surface of a shaping mold. 
     
     
       2. A method of dimensionally stabilizing a transparent, shrinkable layer of polyethylene terephthalate having one or more performance layers or coatings on its surface, said layer being bonded in a draw-formed laminate to at least one layer of plasticized polyvinyl butyral, said method comprising the step of subjecting the laminate to elevated temperature by holding the laminate against the surface of a shaping mold for the laminate for a sufficient time to heat set the polyethylene terephthalate layer. 
     
     
       3. The method of claim 1 or 2 wherein the heat seating step occurs before associating the laminate with glass for forming a safety glazing. 
     
     
       4. The method of claim 3 wherein the draw-formed laminate is capable of conforming to a surface with compound curvature. 
     
     
       5. The method of claim 1 wherein the laminate includes as the performance layer, a multi-layer solar radiation control stack on aside of the thermoplastic layer. 
     
     
       6. The method of claim 5 wherein the surface of the stack or the side of the thermoplastic layer without the stack has been treated or coated to promote bonding to the plasticized polyvinyl butyral. 
     
     
       7. The method of claim 6 wherein the thermoplastic layer comprises polyester film. 
     
     
       8. The method of claim 7 wherein the polyester is polyalkylene terephthalate. 
     
     
       9. The method of claim 8 wherein the polyalkylene is polyethylene. 
     
     
       10. The method of claim 9 wherein the thermoplastic layer is biaxially oriented polyethylene terephthalate. 
     
     
       11. The method of claim 9 wherein the laminate is held against the surface for about 30 sec to 100 min while heating the laminate to about 110° C. to 180° C. 
     
     
       12. The method of claim 11 wherein before forming the laminate the biaxially oriented polyethylene terephthalate layer is heat set at about 200° C. to 250° C. 
     
     
       13. The method of claim 2 wherein the elevated temperature is between 110° C. to 180° C. 
     
     
       14. The method of claim 13 wherein the time is between about 30 sec to 100 minutes. 
     
     
       15. The method of claim 14 wherein the plasticized polyvinyl butyral layer is fusion bonded to the side of the polyethylene terephthalate opposite the side bearing the one or more performance layers or coatings. 
     
     
       16. The method of claim 14 wherein before bonding, the polyethylene terephthalate layer or polyvinyl butyral layer was treated or coated for improving layer adhesion. 
     
     
       17. The method of claim 16 wherein the polyethylene terephthalate layer is about 0.051 to 0.13 mm thick.